media: uvcvideo: document UVC v1.5 ROI

Added documentation of V4L2_CID_UVC_REGION_OF_INTEREST_RECT and
V4L2_CID_UVC_REGION_OF_INTEREST_AUTO.

An example of a userspace implementing this feature can be found at:
https://chromium.googlesource.com/chromiumos/platform2/+/refs/heads/release-R121-15699.B/camera/hal/usb/

Reviewed-by: Ricardo Ribalda <[e-mail]>
Reviewed-by: Sergey Senozhatsky <[e-mail]>
Signed-off-by: Yunke Cao <[e-mail]>
Tested-by: Yunke Cao <[e-mail]>
Reviewed-by: Hans de Goede <[e-mail]>
Signed-off-by: Ricardo Ribalda <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Hans de Goede <[e-mail]>
Signed-off-by: Hans Verkuil <[e-mail]>

Documentation/userspace-api/media/drivers/uvcvideo.rst

···
 	UVC_CTRL_DATA_TYPE_BOOLEAN	Boolean
 	UVC_CTRL_DATA_TYPE_ENUM		Enumeration
 	UVC_CTRL_DATA_TYPE_BITMASK	Bitmask
+	UVC_CTRL_DATA_TYPE_RECT		Rectangular area
 
 
 UVCIOC_CTRL_QUERY - Query a UVC XU control
···
 	__u8	query		Request code to send to the device
 	__u16	size		Control data size (in bytes)
 	__u8	*data		Control value
+
+
+Driver-specific V4L2 controls
+-----------------------------
+
+The uvcvideo driver implements the following UVC-specific controls:
+
+``V4L2_CID_UVC_REGION_OF_INTEREST_RECT (struct)``
+	This control determines the region of interest (ROI). ROI is a
+	rectangular area represented by a struct :c:type:`v4l2_rect`. The
+	rectangle is in global sensor coordinates using pixel units. It is
+	independent of the field of view, not impacted by any cropping or
+	scaling.
+
+	Use ``V4L2_CTRL_WHICH_MIN_VAL`` and ``V4L2_CTRL_WHICH_MAX_VAL`` to query
+	the range of rectangle sizes.
+
+	Setting a ROI allows the camera to optimize the capture for the region.
+	The value of ``V4L2_CID_REGION_OF_INTEREST_AUTO`` control determines
+	the detailed behavior.
+
+	An example of use of this control, can be found in the:
+	`Chrome OS USB camera HAL.
+	<https://chromium.googlesource.com/chromiumos/platform2/+/refs/heads/release-R121-15699.B/camera/hal/usb/>`
+
+
+``V4L2_CID_UVC_REGION_OF_INTEREST_AUTO (bitmask)``
+	This determines which, if any, on-board features should track to the
+	Region of Interest specified by the current value of
+	``V4L2_CID_UVD__REGION_OF_INTEREST_RECT``.
+
+	Max value is a mask indicating all supported Auto Controls.
+
+.. flat-table::
+    :header-rows:  0
+    :stub-columns: 0
+
+    * - ``V4L2_UVC_REGION_OF_INTEREST_AUTO_EXPOSURE``
+      - Setting this bit causes automatic exposure to track the region of
+	interest instead of the whole image.
+    * - ``V4L2_UVC_REGION_OF_INTEREST_AUTO_IRIS``
+      - Setting this bit causes automatic iris to track the region of interest
+        instead of the whole image.
+    * - ``V4L2_UVC_REGION_OF_INTEREST_AUTO_WHITE_BALANCE``
+      - Setting this bit causes automatic white balance to track the region
+	of interest instead of the whole image.
+    * - ``V4L2_UVC_REGION_OF_INTEREST_AUTO_FOCUS``
+      - Setting this bit causes automatic focus adjustment to track the region
+        of interest instead of the whole image.
+    * - ``V4L2_UVC_REGION_OF_INTEREST_AUTO_FACE_DETECT``
+      - Setting this bit causes automatic face detection to track the region of
+        interest instead of the whole image.
+    * - ``V4L2_UVC_REGION_OF_INTEREST_AUTO_DETECT_AND_TRACK``
+      - Setting this bit enables automatic face detection and tracking. The
+	current value of ``V4L2_CID_REGION_OF_INTEREST_RECT`` may be updated by
+	the driver.
+    * - ``V4L2_UVC_REGION_OF_INTEREST_AUTO_IMAGE_STABILIZATION``
+      - Setting this bit enables automatic image stabilization. The
+	current value of ``V4L2_CID_REGION_OF_INTEREST_RECT`` may be updated by
+	the driver.
+    * - ``V4L2_UVC_REGION_OF_INTEREST_AUTO_HIGHER_QUALITY``
+      - Setting this bit enables automatically capture the specified region
+        with higher quality if possible.